thebiotutor.com A2 Biology OCR Unit F215: Control, genomes and environment Module 4.2 Animal responses Notes & Questions Andy Todd 1
Discuss why animals need to respond to their environment. Animals need to be able to coordinate a vast set of responses if they are to stay alive These range from voluntary muscle actions to enable fight or flight to the fine control of balance, posture and temperature regulation Outline the organisation of the nervous system in terms of central and peripheral systems in humans. & Outline the organisation and roles of the autonomic nervous system. The nervous system allows humans to be receptive to their internal and external environment, make sense of the stimuli and respond to these stumli in a way that improves their chances of survival The nervous system comprises of a central and peripheral system that must work together to bring about these response to the stimuli The Nervous System Central Nervous System CNS Peripheral Nervous System PNS Made up of Billions of neurones Grey matter unmyelinated White matter - myelinated Motor Neurones CNS Effectors (muscles & glands) Sensory Neurones Receptor CNS myelinated Autonomic System CNS Smooth muscle Cardiac muscle Glands Unconscious control Non-myelinated 2 plus neurones involved Ganglion present Somatic System CNS Skeletal muscle Conscious control Myelinated 1 neurone involved Parasympathetic pathway Relaxation Pre-ganglionic neurone vary Ganglion close to target tissue Acetylcholine Decrease heart rate Pupil constricts Sympathetic pathway Stress Short pre-ganglionic neurone Ganglion close to Spinal cord Nor-adrenaline Increase heart rate Pupil Dilates Andy Todd 2
Describe, with the aid of diagrams, the gross structure of the human brain, and outline the functions of the cerebrum, cerebellum, medulla oblongata and hypothalamus. Structures Cerebrum o Largest part of the brain o Divide into two hemispheres Cerebral Cortex o Outer surface of the cerebrum o Thin layer of nerve cells o More highly developed in humans than any other organism Cerebellum o Over half the neurones in the brain Corpus Callosum o Holds the two cerebral hemispheres Medulla Oblongata o Found in the inner brain near the top of the spinal cord Hypothalamus o Found in the inner brain Functions Cerebrum o Associated with being Human o Higher brain function Conscious thought Emotional responses Overriding of reflexes Reasoning and Judgement Cerebral Cortex o Divided into regions o Sensory areas Receive impulses directly from sensory receptors o Association areas Compares inputs from previous experiences in order to interpret what the input means and judge an appropriate response o Motor areas Sends impulses to effectors (muscles and glands) Andy Todd 3
Cerebellum o Motor processing Fine control of muscular movements Body posture Balance Dexterity Non-conscious operations E.g walking or driving a car etc o Sensory processing The retina neurones Balance organs in the inner ear Receptors from joints Medulla Oblongata o Controls breathing rate (respiratory centre) o Controls smooth muscle o Controls Heart rate (cardiac centre) Hypothalamus o Controls the autonomic nervous system o Controls the endocrine glands o Homeostatic mechanisms corpus callosum cerebrum Front thalamus hypothalamus pituitary body cerebral cortex pineal body corpora quadrigemina medulla oblongata cerebellum Andy Todd 4
Cerebrum A Pituitary B gland Cerebellum C DMedulla Oblongata Andy Todd 5
Describe the role of the brain and nervous system in the coordination of muscular movement. Functions of the Cerebellum Maintaining muscle tone and posture Coordination of voluntary motor activity Maintenance of balance Cerebellum and Muscle Tone The cerebellum has neural connections with other parts of the brain and the peripheral parts of the body. So at any given moment it continuously receives sensory information from the bones, joints and muscles about their position, rate and direction of movement and forces acting on them. The cerebellum in turn conveys this information to the motor control centers of the cortex (motor cortex) setting the background tone and posture so that the cortex can execute new movements based on intent. In other words, the cerebellum tells the motor cortex in what position a limb already is and what it is doing so the cortex can plan its next move. Andy Todd 6
Cerebellum and Motor Control The cerebellum also continuously receives information on the sequence of movements desired by the motor control areas of the cortex. With regard to movement coordination, the cerebellum behaves like a computer, constantly comparing the actual movement of the muscle groups with the motions intended by the motor cortex. In case of a difference between the two, the cerebellum immediately sends signals to the muscle groups to correct the movement so that the desired effect can be achieved, much like computers calculating and correcting the flight path of airplanes or space vehicles. Andy Todd 7
Describe how coordinated movement requires the action of skeletal muscles about joints, with reference to the movement of the elbow joint. The Elbow Joint Muscle that control the elbow joint Andy Todd 8
Operation of the neuromuscular junction Explain, with the aid of diagrams and photographs, the sliding filament model of muscular contraction. The skeletal muscle has contractile organelles called microfibrils These microfibrils contract by sliding filaments over each other Each microfibril is made up of many microfilaments of which there are two types Andy Todd 9
Myosin filaments o Myosin (or thick Myosin) filaments contain many myosin molecules o Two globular heads o One tail Actin Filaments o Consists of two actin filaments (F-actin) wrapped around each other o Each actin filament is made of individual globular actin monmers (G-actin) o The two actin filaments are held together by Tropomyosin a rod shaped protein o The thin actin filament also includes Troponin which has 3 polypeptides One to bind to G-actin One to bind to tropomyosin One to bind calcium ions Andy Todd 10
Arrangements of these filaments Andy Todd 11
Relaxed Muscle Contracted Muscle A Band (Myosin Filament) Same length Same Length I Band (Band of no over lap - Actin Only) Longer Shorter H Band (Band of no over lap - Myosin Only) Longer Shorter Sarcomere (from Z-line to Z-line) Longer Shorter Andy Todd 12
The Power stroke An action potential reaches the dendrite at a neuromuscular junction Acetylcholine is released by exocytosis into the junction and binds to complementary receptors on the sarcolemma The wave of depolarisation travels along the sarcolemma nad down transverse tubules (T-systems) This wave of depolarisation down the tubule excites the sarcoplasmic reticulum. The sarcoplasmic reticulum releases calcium ions into the cytoplasm Calcium ions are involved in two processes o Binding to troponin o Activating ATPase Calcium firstly binds to troponin Troponin shifts out of its default position and as it does so it pulls tropomyosin with it This exposes the actin myosin binding site that is blocked when the tropomyosin is in its default position The myosin head can now bind to the actin filament, forming a CROSS BRIDGE Meanwhile other calcium ions have activated the enzyme ATPase which catalyses the hyfrolysis of ATP ADP + Pi releasing energy This energy moves the myosin head at the hinge region pulling the thin actin filament over the think myosin filament = POWER STROKE The cross bridge is stable and so ATP needs to bind to the myosin filament to provide energy to break the cross bridge Now the cross bridge is broken the myosin head can bind to another actinmyosin binding site forming another cross bridge further along the actin filament. This only occurs if there is enough calcium ions and ATP molecules If either ATP or calcium ions are limiting then the filaments slide back to their starting positions and the muscles relaxes Andy Todd 13
Outline the role of ATP in muscular contraction, and how the supply of ATP is maintained in muscles. ATP comes from three sources o Aerobic respiration Requires Oxygen and respiratory substrate Produced rapidly in the many mitochondria o Anaerobic respiration Produced quickly in the sarcoplasm Leads to a build up of lactic acid Leads to an increase of blood to the muscles o Phosphocreatine (PCr) Donates phosphate to phosphorylate ADP ATP Phosphocreatine Creatine Phosphotransferase P ADP ATP Phosphocreatine Andy Todd 14
Compare and contrast the action of synapses and neuromuscular junctions. Neuromuscular Junction Synapse Neuromuscular Junction Neurotransmitter is acetylcholine Acetylcholinesterase breaks down neurotransmitter Between neurone and muscle Post junction membrane is clefted Many receptors Needs one action potentials to cause depolarisation on post synaptic membrane Synapse Various neurotransmitters Various enzymes breaks down the neurotranmitters Between two neurones Post synaptic membrane is smooth Fewer receptors Needs many action potentials to cause depolarisation on post synaptic membrane Similarities Both release neurotranmitter by exocytosis Calcium ions cause vesicles to migrate and fuse with prejunction membrane Neurotransmitter crosses synapse by diffusion Both post junction membranes have sodium channels Andy Todd 15
Outline the structural and functional differences between voluntary, involuntary and cardiac muscle. Involuntary (Smooth) Muscle Cardiac Muscle Voluntary (Skeletal) Muscle Not Striated Striated Striated Uninucleated Multinucleated Multinucleated Contracts slowly Contracts quickly Contracts quickly Fatigues slowly Does not fatigue Fatigues quickly Unconscious control Unconscious control Conscious control Single cells Cells branch and interlink Cells in fibres Found in Walls of interstines, arteries, bonchioles and the iris of the eye spindle shaped Found in the heart Intercalary discs with free ions Found in muscles that move the skeleton Contain micrfibrils Andy Todd 16
Skeletal Muscles Andy Todd 17
Smooth Muscles Andy Todd 18
Cardiac Muscles Andy Todd 19
State that responses to environmental stimuli in mammals are coordinated by nervous and endocrine systems. & Explain how, in mammals, the fight or flight response to environmental stimuli is coordinated by the nervous and endocrine systems. Sensory Receptors Cerebral Cortex Hypothalamus Releases CRF Corticosteroid Releasing Factor Sympathetic pathway Anterior Pituitary Gland Glands & Smooth muscles Iris Gut Wall Heart rate Sweat Hairs Adrenal Gland Adrenal Cortex Adrenal Medulla Releases ACTH AdrenoCorticoTropic Hormone Releases Adrenaline Releases 30 different hormones Blood stream Physiological Changes Increase heart rate Increase Ventilation Increase Blood Glucose Increase Sweating Increase Pupil dilation Dilate arterioles of the liver and muscles Constrict arterioles of the digestive system Andy Todd 20
Questions 1. Below is a drawing of the brain that shows the origin of the cranial nerves. A B C D (a) State the direction from which the brain has been drawn. [1] (b) (i) Name the structures A, B, C and D shown on the diagram. A... B... C... D... [4] (ii) State two roles of structure D. 1... 2... [2] Andy Todd 21
(c) The hypothalamus constantly monitors and regulates the concentration of hormones in the blood. Outline how the hypothalamus regulates the concentration of hormones in the blood. [2] [Total 9 marks] 2 Calcium ions are necessary for the contraction of rabbit s striated muscle. Describe the role played by calcium ions in the contraction of striated muscle. [Total: 3 marks] 3 The figure below shows a section through a human elbow joint. humerus ligament synovial membrane A B ulna Andy Todd 22
(i) Name A and B. A... B... [2] (ii) Describe the roles of A and B in the movement of the elbow joint. [3] [Total 5 marks] 4 The cerebellum and medulla oblongata are regions of the brain. The cerebellum is concerned with the control and coordination of movement and posture. Suggest why the cerebellum of a chimpanzee is relatively larger than the cerebellum of a cow. [Total: 2 marks] Andy Todd 23
5 The figure below shows a vertical section through the human brain. corpus callosum cerebrum Front thalamus hypothalamus pituitary body cerebral cortex pineal body corpora quadrigemina medulla oblongata cerebellum (i) Name the structure shown above that links the two cerebral hemispheres.... [1] (ii) The table below shows the functions of some areas of the brain. Complete the table using the labels in the figure above. area of brain example of function... co-ordination of posture... control of heart rate... control of temperature regulation... control of speech [4] [Total 5 marks] Andy Todd 24
6 In this question, one mark is available for the quality of use and organisation of scientific terms. The following figure shows a neuromuscular junction. motor neurone mitochondrion pre-synaptic membrane synaptic cleft post-synaptic membrane myofibril The figure above shows that mitochondria are present on both sides of the synaptic cleft. Explain why mitochondria are essential for the transmission of impulses across the cleft and for muscular contraction. transmission of impulses across the cleft... Andy Todd 25
muscular contraction... [8] Quality of Written Communication [1] [Total 9 marks] 7 (a) The cerebellum and medulla oblongata are both parts of the hindbrain. Outline the functions of these two parts of the brain. cerebellum [2] medulla oblongata [2] Andy Todd 26
(b) Alzheimer s disease is characterised by several changes in the cerebrum, including tangles inside neurones and plaques between neurones. State what causes (i) tangles;......... (ii) plaques.......... [2] Another change in the cerebrum of a person with Alzheimer s disease is a decrease in acetylcholine released by neurones that form memory circuits. During a clinical trial, people with Alzheimer s disease were treated with a drug that inhibited the enzyme acetylcholinesterase. This improved their short-term memory. (c) Suggest how the drug may inhibit acetylcholinesterase. [3] Andy Todd 27
(d) Suggest how the drug improves short-term memory. [2] (e) State three precautions that should be taken when designing such clinical trials, to ensure that any effects are due to the drugs being tested. 1... 2... 3... [3] [Total 14 marks] Andy Todd 28